In recent years, the widespread availability of camera phones having a camera function has increased the opportunities for users to photograph various kinds of photographic subjects. For example, a photographic subject at a distance from the camera lens, such as a friend or scenery, is photographed (normal snapshot) or a photographic subject at a close distance from the camera lens, such as a bus time schedule or flower petals, is photographed (close-up photography).
For close-up photography (macro photography), the camera lens needs to be positioned slightly closer to the photographic subject that for a normal snap shot. Therefore, a photographing lens system of this kind is equipped with a drive mechanism that drives the lens to be displaced in the optical axis direction; by switching a switch, the drive mechanism is driven to move the lens in the optical axis direction (see Japanese Patent Application 2006-259032 Unexamined Publication, for example).
The lens driving apparatus disclosed in Japanese Patent Application 2006-259032 Unexamined Publication comprises a holder, a yoke that supports the holder to be displaced in the optical axis direction and a pair of flat springs that sandwich the holder in the top-bottom direction. In such a configuration, while current is applied to the coils to generate electromagnetic force, the flat springs are used to generate a recovery force that opposes the electromagnetic force; by adjusting the relative strength of these two forces, the position of the holder is regulated.
The above-mentioned yoke is a magnetic body so that it can function as part of a magnetic circuit. To increase magnetic efficiency even more, a ceiling portion of the lens driving apparatus, the front end face of the apparatus opposite from the imaging device, is also a magnetic body.
However, with the above-described configuration, when the holder is moved in the optical axis direction (when the holder is moved orthogonally with respect to the above-mentioned ceiling portion), the moving distance of the sleeve when current is applied to the coils may be inconsistent.
At least an embodiment of the present invention is devised considering the above problem, and it provides a lens driving apparatus capable of preventing inconsistent moving distance of the sleeve when current is applied to the coils.